1. Field of the Invention
The present invention relates to a fixing apparatus used with an image forming system such as a laser beam printer, copying machine and the like.
2. Related Background Art
An example of a conventional fixing apparatus is shown schematically in FIG. 1.
A fixing roller 1 is formed by coating an insulative layer 3 made of fluororesin, silicone resin and the like on a rigid metallic roller, and a pressure roller 2 presses against the fixing roller 1. A recording medium which bears a toner image formed by electrophotography is passed between the fixing roller 1 and the pressure roller 2, so that the toner image is fixed onto the recording medium. Further, in the apparatus shown in FIG. 1, a DC voltage is applied between the fixing roller 1 and the pressure roller 2 so that the fixing roller contacting the toner image has the same polarity as the toner image.
In this way, an electrostatic repelling force is generated between the fixing roller and the toner image, thereby preventing the occurrence of a so-called xe2x80x9coffset phenomenonxe2x80x9d, where the toner adheres to the fixing roller.
However, in the above-described conventional fixing apparatus, adequate insulation is not obtained, and the offset phenomenon is not completely prevented, depending upon the surface condition of the fixing roller and the material of the insulative layer.
The present invention aims to eliminate the above-described drawbacks. An object of the present invention is to provide a fixing apparatus wherein the offset phenomenon does not occur between the fixing roller and the toner.
Another object of the present invention is to provide a fixing apparatus wherein the transfer blank phenomenon can be prevented.
A further object of the present invention is to provide a fixing apparatus which can stabilize a potential on the recording medium.
A still further object of the present invention is to provide a fixing apparatus which can suppress the generation of noise due to leakage of the bias of a fixing roller.
Other objects of the present invention will be apparent from the following description referring to the accompanying drawings.